Joining Pieces in an Imported STL File

Hello.

I’m new to 3D modeling (so please bear with me if I’m dumb), but I wanted to have something (a sword hilt) 3D printed, so I took a free model from online and imported it as an STL file, and then modified it for my purposes.

I sent the piece out to be printed professionally, and they sent me this response:

“I am guessing that you built one side of this handle in a half and then mirrored it? When that was done, I do not think you united/joined the two halves to be one solid body. When this happens, a gap between halves is sometimes created and the part will not print correctly. Please go back and ensure this part is one solid body.”

I never mirrored anything, so I’m guessing that the problem must be an underlying one in the model I used, however, since I imported it from an STL file, the original model all shows up as one object, and a join mesh operation doesn’t do anything.

Is there some other operation that I don’t know about that would work, or would I need the original design file in order to fix this problem?

Thanks in advance for any helpful advice.

Nightshadowaotc

First thing to do (something it appears many people simply fail to do when there is an apparent issue) is actually look at the mesh, move some vertices along the centre line, are they all connected etc

In edit mode try Select / Non Manifold menu to identify potential issues
You can merge overlapping vertices by selecting them and W / remove doubles (adjust merge distance in toolshelf)

You need to do all this yourself since you haven’t supplied any blend file for review

Thanks a lot for your help!

I will try this - it sounds like this should solve my problem.